WSJ: Numbers Guy

The Numbers Guy examines numbers in the news, business and politics. Some numbers are flat-out wrong or biased, while others are valid and help us make informed decisions. Carl Bialik tells the stories behind the stats, in daily updates on this blog and in his column published every other Friday in The Wall Street Journal. Carl, who holds a degree in mathematics and physics from Yale University, also cowrites The Daily Fix, a sports column on WSJ.com. He welcomes your comments at .

Retirement Calculators, Assumptions and Statistical Methods Retirement calculators employ different assumptions to help users predict whether their rate of savings will support their current lifestyle after they quit work.
Boomers, Gen Xers and Millennials: Catchall Groupings Generational groupings are attractive to academics who want to measure social and cultural change. They’re coveted by marketers looking to capitalize on evolving consumer tastes. And they appeal to others seeking to exploit the perceived psyche of the different groups.
Economists’ Enemy: Residual Seasonality When seasonally adjusted numbers continue to exhibit the influences of seasonal effects, much as first-quarter readings on gross domestic product have regularly been doing, statisticians refer to it as residual seasonality. And that effect hampers seasoned economists from making clear-eyed judgments on the strength of the economy.
How Math Helps Fight Epidemics Like Zika When an epidemic such as Zika threatens to sweep across the country, public-health workers and policy makers need some basic information in order to plan a strategic response to make the best use of limited resources to protect the public from the spread of the disease. Enter the mathematicians and statisticians.
Joe DiMaggio’s Streak (Predictably) Survives Jackie Bradley Jr.'s bid to supplant Joe DiMaggio atop the Major League Baseball hit-streak list ended at 29 games. That's not surprising as many observers consider Joltin' Joe's streak the most difficult record to break in sports.
Behind The Numbers: Beating DiMaggio’s Streak From the Armchair MLB.com really wants to give away $5.6 million. But there’s a catch: To claim the prize, one needs to participate in Major League Baseball’s Beat the Streak contest and assemble a batting streak that surpasses Joe DiMaggio’s run of 56 consecutive games in 1941. This isn't easy.
Why Some Cicadas Have Reason to Brood: Potential Extinction ​Periodical cicadas live underground for 13 or 17 years before emerging to mate, lay eggs and die off, and today, there are 15 known broods in the U.S. There used to be 16 and the current number may dwindle if the teetering Brood VII goes extinct.
Facetime With Uncle Sam A number of government surveys are conducted in face-to-face interviews for a variety of reasons. Sometimes, physical material must be collected or the survey is too long and complex to conduct by telephone or mailed questionnaire. The results are some of the richest and most complete survey data available.
The Challenging Calculus of Figuring Out Who Gets to Vote The litigants in a recent Supreme Court case suggested using the American Community Survey, an annual sample of 2.5% of U.S. households that asks about citizenship, to estimate the citizen voter-age population.
Behind The Numbers: Researching Hailstorms Hailstorm data help meteorologists improve forecasts, insurers assess damages and businesses and citizens minimize exposure.